Feed stroke changing device for transfer feeder

ABSTRACT

For a transfer feeder for use in a transfer press having a plurality of work stations in a press machine body, having a plurality of cross bars arranged as spaced apart from one another in a feed direction and operative to move two-dimensionally by a feed means and a lift means, and an attractive means carried by each of the cross bars for attractively holding a workpiece and movable therewith for transferring the workpiece into and from one of the work stations to another sequentially, a feed stroke varying apparatus is disclosed which comprises: a pair of lift beams adapted to be raised and lowered by the lift means; a plurality of cross bar carriers carried as spaced apart from one another by the pair of lift beams in the feed direction and each constructed of a principal carrier and a subsidiary carrier; a coupling means for interconnecting such principal carriers; a link member for connecting to the feed means one of the principal carriers which is located at a most upstream side thereof; a feed stroke changing means arranged between a said principal carrier and a said subsidiary carrier for changing a distance relative between them to alter a stroke of feed performed by the cross bars; and a control means for controlling an operation of the feed stroke changing means, each of the cross bars being detachably bridged across a pair of the subsidiary carriers opposed to each other, the feed means being adapted to reciprocate the cross bars in the feed direction, the feed stroke changing means being adapted to alter the feed stroke of the cross bars.

TECHNICAL FIELD

The present invention relates to a feed stroke varying apparatus for atransfer feeder for use in a transfer press in which a vacuum (suction)type work carrier system is employed.

BACKGROUND ART

A conventional transfer press having a plurality of work stations in apress machine main body is equipped with a transfer feeder and isconstructed to transfer a workpiece sequentially into the successivework stations therewith.

Such a transfer feeder typically includes a pair of transfer bars whichare arranged in parallel so as to extend in a feed direction. Aplurality of cross bars each having a work suction means which isadapted to hold the workpiece are bridged transversely across thetransfer bars to lie equidistantly spaced apart from one another in thefeed direction. In operation, the transfer bars are driven twodimensionally both in the feed direction and in the lift direction toallow the workpiece to be transferred into and from one of the workstations into another in sequence.

In a transfer feeder as described above, a feed cam is rotated by apower taken from the press main body to cause a feed lever to be swungso that the above mentioned transfer bars which are mechanically coupledto the feed lever may be driven in the feed direction. With such aconstruction adopted, the transfer feeder of this type provides a feedstroke that is definitely determined by a particular profile of the feedcam, which therefore cannot be changed without exchanging the feed cam,and hence has been found to be inconvenient.

In order to take into account such an inconvenience, there has beenproposed, e. g., in Japanese Unexamined Patent Publication No. Sho61-115633 or Japanese Unexamined Utility Model Publication No. Sho64-5719, a workpiece transfer apparatus that is designed to allow thefeed stroke of a cross bar to be altered.

A workpiece transfer apparatus as described in these publicationsincludes a pair of feed bars (which correspond to the transfer barsmentioned) extending in the feed direction each of which is providedwith a slide member that is slidable in the feed direction. A cross baris there bridged transversely across a pair of such slide members whichare juxtaposed with each other to provide a feed stroke that can berendered variable when they are displaced in the feed direction by acylinder drive unit to allow them to move relative to the feed bars.

A workpiece transfer apparatus as proposed in these publications has,however, been found to be yet inconvenient because of the constructionin which a guide means for guiding the feed bars in the feed directionand a guide means for guiding the slide members slidably need to bearranged to be vertically separate. This requires the structure for theboth placed to be greater in height to the extent that the field of viewand the visibility for the inside of the press machine may substantiallybe lost by the slide members, the cylinder drive unit and so forth.

An increase in height of the press machine body also results in anincreased backlash or looseness thereof in the vertical direction, whichtends to cause the cross bars to be vibrated, bringing about anaccidental fall of the work from the work suction means and further afailure in or an incorrectness of feed.

A transfer feeder must also be used wherein the path in which aworkpiece is transferred (path line) can in height be varied in severallevels depending on the sizes and shapes of particular workpieces. Ifthe path line is to be altered in the transfer feeder, it, too, has beenfound to be defective because of the development of an error in feedstroke and the inability to suck a proper position of a workpiece withthe suction means for reasons as mentioned below.

Specifically, the structure in which a feed lever and a cross barcarrier are coupled together by a linkage having a given length causes achange in height of the cross bar carrier with the feed lever halted toresult in a circular motion of the point at which the link member andthe cross bar carrier are pivotally connected together about the pointat which the link member and the feed lever are pivotally connectedtogether.

A change in height of the path line may, therefore, cause the cross barcarrier to be displaced in the feed direction, bringing aboutinconveniences represented by the development of an error in feedstroke. Consequently, the suction means becomes unable to attract andthereby to hold a workpiece as properly positioned, which thus tends tobe incorrectly fed in the path line or cannot be transferred into a workstation accurately at a given location.

In an attempt to resolve such problems, a corrective apparatus for atransfer feeder has been proposed in which a height adjustment means isprovided at a site where the link member and the cross bar carrier arecoupled together so that if the path line is varied in height thepivotal point at which the link member and the cross bar carrier areconnected together may be vertically adjusted in position by the heightadjustment means, thus that there may be no error in feed stroke.

The corrective apparatus proposed has yet been found to bedisadvantageous, however, in that it involves a substantial increase incost arising from the need for a height adjustment motor means and it isalso inconvenient for the requirement of a space for accepting theheight adjustment means where the link member and the cross bar carrierare coupled together.

It is accordingly an object of the present invention to eliminate thesedisadvantages in the prior art and to provide a variable feed strokefeeder apparatus for a transfer feeder which permits the feed stroke tobe altered without difficulty and assures a good visibility in the pressmachine body, yet without permitting a change in height of the path lineto develop an error in feed stroke.

SUMMARY OF THE INVENTION

In order to achieve the above mentioned object, there is provided inaccordance with the present invention in a certain aspect thereof a feedstroke varying apparatus for a transfer feeder for use in a transferpress having a plurality of work stations in a press machine body, thetransfer feeder having a plurality of cross bars arranged as spacedapart from one another in a feed direction and operative to movetwo-dimensionally by a feed means and a lift means, and an attractivemeans carried by each of the cross bars for attractively holding aworkpiece and movable therewith for transferring the workpiece into andfrom one of the work stations to another sequentially, the feed strokevarying apparatus comprising: a pair of lift beams adapted to be raisedand lowered by the said lift means; a plurality of cross bar carrierscarried as spaced apart from one another by the said pair of lift beamsin the feed direction and each constructed of a principal carrier and asubsidiary carrier; a coupling means for interconnecting such principalcarriers; a link member for connecting to the said feed means one ofsaid principal carriers which is located at a most upstream sidethereof; a feed stroke changing means arranged between a said principalcarrier and a said subsidiary carrier for changing a distance relativebetween them to alter a stroke of feed performed by the said cross bars;and a control means for controlling an operation of the said feed strokechanging means, wherein each of the said cross bars is detachablybridged across a pair of the said subsidiary carriers opposed to eachother; the said feed means is adapted to reciprocate the said cross barsin the feed direction, and the said feed stroke changing means isadapted to alter the feed stroke of the said cross bars.

According to the construction described above, it can be noted andshould be understood that changing the relative distance between theprincipal carrier and the subsidiary carrier by the use of a feed strokechanging means enables the feed stroke of the cross bars to be alteredas desired and hence, even if the work stations are not spacedequidistantly, enables a workpiece to be transferred into themsequentially and in succession without any trouble.

It can also be noted and should also be understood that changing thefeed stroke of the cross bars during a feed operation enables aworkpiece to be transferred without the workpiece, the workpieceattracting means or the cross bars interfering with a die or a slide,thereby reducing an area of possible interference and hence increasesthe degree of freedom of designing a series of dies. Also, since thestructure of the die itself can be simplified, there results asubstantial saving in the cost of press dies.

In the construction described, it is desirable that the said feed strokechanging means comprise a servo cylinder assembly having a first endconnected to the said principal carrier and a second end connected tothe said subsidiary carrier.

It is also desirable that the said feed stroke changing means comprise:a rack having one end connected to one of the said principal carrier andthe said subsidiary carrier, and a pinion in mesh with the said rack andadapted to be driven by a rotational drive source mounted to the otherof the said principal carrier and the said subsidiary carrier.

It can be seen and should be appreciated that the construction justmentioned above enables the feed stroke to be readily and smoothlyaltered even in the course of a feed operation and hence to be changedwith precision.

In the construction first described above, it is desirable that the saidprincipal carrier and the said subsidiary carrier are suspended from alower side of said lift beam so as to be capable of reciprocating.

It can be noted and should be understood that the construction justdescribed above enables a single guide rail or a single set of guiderails to be used for both the principal and subsidiary carriers, andaccordingly can lower in height a guide rail assembly as in the priorart which is to be arranged in two levels, while substantially improvingthe field of view or visibility in a vertical direction of the liftbeams.

An improvement in the field of view and visibility for the inside of apress machine main body that results can be seen and should be noted toenable the observation of a press-forming operation to prevent adefective product from occurring. Also, a reduction in height of thesystem and further a reduced backlash or looseness of components in thevertical direction minimize any vibrations which may be created in thecross bars, thus eliminating an inconvenience as met in the prior art, acause resulting in the accidental fall of a work from the workattracting means or the occurrence of a failed or incorrect feed.

Further in the construction first mentioned above, it is desirable thatthe control means be responsive to an error in feed stroke resultingfrom a change in transfer press path line as caused by a change inheight of the cross bars and be operative to act to expand or extend andcontract or retract the said feed stroke changing means so as to correctsuch an error.

According to the construction just described above, it can be seen andshould be understood that a change in the transfer press path line doesnot allow an error to be caused in the feed stroke and hence prevents aworkpiece from being held as mis-positioned to the work holder, frombeing incorrectly fed or from being transferred as mis-positioned into awork station, caused by the inability to attract a proper position of aworkpiece with the workpiece attracting means. In addition toeliminating these and other inconveniences as have been met in the priorart, the specific construction described makes it unnecessary tointroduce a height adjustment means as has been required heretofore tocorrect an error in the feed stroke and thus provides a substantialsaving in both the cost and space entailed in the transfer press.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will better be understood from the followingdetailed description and the drawings attached hereto showing certainillustrative embodiments of the present invention. In this connection,it should be noted that such embodiments as illustrated in theaccompanying drawings are intended in no way to limit the presentinvention but to facilitate an explanation and understanding thereof.

In the accompanying drawings:

FIG. 1 is a front view that shows a transfer press in which a firstembodiment of the variable feed stroke feeder apparatus for a transferfeeder is provided according to the present invention;

FIG. 2 is a top plan view that shows a transfer feeder incorporatingthat the first embodiment of the present invention;

FIG. 3 is a side elevational view taken as viewed in the direction ofthe arrow A in FIG. 1;

FIG. 4 is a bottom plan view that shows cross bar carriers illustratingthe first embodiment of the present invention;

FIG. 5 is an enlarged front view that shows a cross bar carrier that islocated at the most upstream side of the cross bar carrier arrangement,illustrating the first embodiment of the present invention;

FIG. 6 is a side elevational view taken as viewed from the direction ofthe arrow B in FIG. 5;

FIG. 7 is an enlarged front view that shows a cross bar carrier which islocated at a downstream or middlestream of the cross bar carrierarrangement, illustrating the first embodiment of the present invention;

FIG. 8 is a side elevational view taken as viewed from the direction ofthe arrow C in FIG. 7;

FIGS. 9A, 9B, 9C and 9D are each an explanatory view that illustratesthe operation of the first embodiment of the present invention;

FIGS. 10A and 10B are each a functional explanatory view thatillustrates a transfer press in which its path line is being changed;

FIG. 11 is a front view that shows a cross bar carrier upon which asecond embodiment of the feed stroke varying apparatus for a transferfeeder is practiced; and

FIG. 12 is a side elevational view taken as viewed from the direction ofthe arrow D in FIG. 11.

DETAILED DESCRIPTION

Hereinafter, suitable embodiments of the present invention with respectto a feed stroke varying apparatus for a transfer feeder are set forthwith reference to the accompanying drawings hereof.

FIG. 1 is a front view that shows a transfer feeder in which a suction(vacuum) type workpiece attracting and holding system is employed; FIG.2 is top plan view thereof; FIG. 3 is a side elevational view taken asviewed in the direction of the arrow A in FIG. 1; FIG. 4 is a bottomplan view that shows cross bar carriers upon which a first embodiment ofthe present invention relating to a feed stroke varying apparatus for atransfer feeder is practiced in accordance with the present invention;FIG. 5 is an enlarged front view that shows a cross bar carrier; FIG. 6is a side elevational view taken as viewed from the direction of thearrow B in FIG. 5; FIG. 7 is an enlarged front view that shows a crossbar carrier; FIG. 8 is a side elevational view taken as viewed from thedirection of the arrow C in FIG. 7; FIGS. 9A, 9B, 9C and 9D; and FIGS.10A and 10B are each a functional explanatory view that illustrates anoperation.

The transfer feeder shown in FIGS. 1 through 3 is equipped in the pressmachine main body of a transfer press and has a pair of lift beams 2arranged in a feed direction thereof (i. e. an X-axis direction). Thelift beams 2 are capable of being displaced vertically in a liftdirection thereof (i. e. a Y-axis direction) by a plurality of liftmeans 3 which are arranged as spaced apart from one another in the feed(X-axis) direction.

The lift means 3 includes a lift motor 3a (a servo motor) and has apinion 3b rotated both normally and reversely by the lift motor 3a.

Each of such pinions 3b is in mesh with a rack 3d formed on a liftingrod 3c so that a rotation of the pinions 3b may cause the respectivelifting rods 3c at the same time to be moved vertically in the lift(Y-axis) direction. The lifting rods 3c have their respective lower endsconnected to either of the two lift beams 2 so that a vertical movementof each of the lifting rods 3c may cause the lift beams 2 both ahead andbehind thereof at the same time to be moved vertically.

Each of the lift beams 2 has a plurality of cross bar carriers 4arranged as spaced apart from one another on the feed (X-axis)direction.

As shown in FIG. 4, each of the cross bar carriers is divided into aprincipal carrier 4₁ and a subsidiary carrier 4₂ and has two ends onwhich are supported a pair of rollers 5 as rotatable, respectively.Positioned between these rollers 5 are a pair of guide rails 2a whichproject at a pair of lower sides of the lift beams 2, respectively. Theprincipal carriers 4₁ and the subsidiary carrier 4₂ are suspendeddownwards from the lift beams 2 so as to be displaceable in the feed(X-axis) direction along the guide rails 2a, respectively.

As shown in FIG. 4, adjacent principal carriers 4₁ are connectedtogether by a pair of connecting rods 6 beneath the lift beams 2 and arecapable of being reciprocated at the same time by a feed means 20, whichwill be described later, in the feed (X-axis) direction.

A support bracket 4a is mounted to the lower surface of each of theprincipal carriers 4₁ at its upstream side as projecting therefrom andhas the base end side of a feed stroke changing means 7 pivotallyconnected thereto by means of a pin 8.

The feed stroke changing means 7, for example, is constituted by a servocylinder assembly 7b wherein the forward end of a piston rod 7aprojecting from the forward end of the servo cylinder assembly 7b intothe subsidiary carrier (4₂) side is pivotally connected by means of apin 9 to a bracket 4b which is mounted to the lower surface of each ofthe subsidiary carriers 4₂ at its upstream side as projecting therefrom.In this fashion, the principal carrier 4₁ and the subsidiary carrier 4₂in each of the cross bar carriers 4 are coupled together by the feedstroke changing means 7 according to the embodiment here shown.

There is also mounted a tilt means 10 to the lower surface of each ofthe subsidiary carriers 4₂ as extending in a direction orthogonal to thefeed (X-axis) direction.

A rotary shaft 10a of each of the tilt means 10 is arranged to projectinto the sides of the subsidiary carriers 4₂ which are juxtaposed witheach other, and the two ends of a cross bar 12 is removably supported onthe rotary shaft 10a of the tilt means 10 on the pair of those mutuallyjuxtaposed subsidiary carriers 4₂.

The cross bar 12 may be constituted by an elongate angular steel tubeand a plurality of such tubes may as shown in FIG. 2 be arranged asspaced apart from one another in the feed (X-axis) direction, permittingconnecting members 12a mounted to their respective two ends to becoupled to the respective two ends of the rotary axes of the tilt means10. Each of the cross bars 12 has a plurality of work attracting means13, each of which may be constituted by a suction cup, detachablymounted thereto via a like plurality of support arms 13a, respectively,so that a workpiece 14 may be attracted by such a work attracting means13 in each of the work stations W1, W2, W3, . . . .

On the other hand, the principal carrier 4₁ of the one of cross barcarriers 4 which is located at a most upstream side thereof has mountedto its end surfaces a pair of connecting pieces 16 as projectingtherefrom as shown in FIGS. 5 and 6, and to each of which one end sideof a link member 18 is pivotally connected via a pin 17.

The link member 18 is positioned over the two opposite sides of the liftbeams 2 and has the other end side coupled to the lower end of a feedlever 20a of the feed means 20 which is disposed at an upper upstreamside of the press machine main body 1.

The feed means 20 has a cam shaft 20b which is adapted to be rotated bya power as taken from a slide drive mechanism (not shown). A feed cam20c secured to the cam shaft 20b allows the lower end of the feed lever20a to be swung in the feed (X-axis) direction about the support portionfor its upper part as a center, thereby causing the cross bar carriers 4at the same time to be reciprocated in the feed (X-axis) direction viathe link member 18.

It should be noted that a piping arrangement (not shown) for supplyingpower in the form of a pressurized hydraulic or pneumatic fluid into thefeed stroke changing means 7, the tilt means 10 and other parts asmounted to the cross bar carriers 4 and electric cables (not shown) fortransmitting signals from various sensing means as mounted to the crossbar carriers 4 as well as for supplying electric power may be receivedin a cable bearer 21 as shown in FIGS. 5 though 8. Also, the lift means3 and the feed stroke changing means 7 are adapted to be controlled by acontrol means.

The operation of the transfer feeder constituted above is explained asfollows.

A workpiece 14 in the form of a plate to be press-formed is introducedfrom an upstream side (left side in FIG. 1) of the press machine mainbody 1 and transferred by a work transfer means 22 into a first workstation W1.

Next, power taken from the slide drive mechanism of the press main body1 is used to rotate the feed cam 20c, causing the feed lever 20a to beswung. This allows the cross bar carriers 4 connected via the linkmember 18 to the feed lever 20a to be displaced towards their upstreamside. At the same time the lift means 3 are driven to raise the liftbeams 2. Then, the cross bars 12 which have been held at a presetstand-by position Z that is an approximate midway point of the wholefeed stroke of the transfer feeder as shown in FIG. 9A are allowed to bedisplaced along a pattern path as shown in FIG. 9A to a position abovethe workpiece where it is lowered. The work attracting means 13 attachedto the cross bar 12 located at the most upstream side acts to attractthe workpiece 14 having been transferred into the first work station W1whereas the work attracting means 13 located at a site downstream ofthat side is allowed to attract a workpiece 14 having been press-formedin a succeeding work station W2, W3, . . . .

Thereafter, the lift means 3 raises the lift beams 2 causing the crossbars 12 to be raised as well, along the patterned path indicated in FIG.9A. And, where the workpiece 14 attracted by the work attracting means13 arrives at the vicinity of the path line P, the feed lever 20a beingreciprocated causes the cross bar carrier 4 to be displaced in the feed(X-axis) direction to allow the cross bars 12 to commence an advancing.

During the cross bar's advancing operation, the control means acts toelongate (extend) the feed stroke changing means 7, for example, by 100mm, to cause the subsidiary carrier 4₂ relative to the principal carrier4₁ to move, by 100 mm, downstreams. Then, where the workpiece 14 arrivesat a site above a succeeding work station W2, W3, . . . , the lift means3 lowers the lift beams 2 so that the cross bars 12 may be lowered alongthe patterned path shown in FIG. 9A to transfer the workpiece 14 intothe work station W2, W3, . . . .

Subsequently, when the work attracting means 13 releases the workpiece14, the cross bars 12 commence returning. Then, a contraction(retraction) of the feed stroke changing means 7 by 100 mm causes thesubsidiary carrier 4₂ relative to the principal carrier 4₁ to bedisplaced by 100 mm upstreams to return the cross bars 12 to the initialstand-by position Z and to bring it a halt there.

Thereafter, a repetition of the operation mentioned above in synchronismwith the operation of the press machine body 1 causes the workpiece 14transferred therein to be sequentially worked (formed) in the workstations W2, W3, . . . , in succession, permitting the workpiece 14 thathas undergone all the working operations to be eventually transferredout of the press machine body 1.

It should be noted that the feed stroke is altered in the abovementioned example specifically by using as the feed stroke changingmeans 7 a cylinder assembly which is designed to extend (or expand orelongate) and retract (or contract), herein generally referred to simplyas "deform". In the example described, it can be seen that any ofvarious patterned paths other than that shown in FIG. 9A for themovement of the cross bar 12 may be alternatively employed.

For example, a patterned path as indicated in FIG. 9B is obtained forthe cross bar 12 by permitting the feed stroke changing means 7 toretract or contract by 100 mm when the cross bar 12 is returned from thestand-by position Z to the upstream and to extend or elongate by 100 mmin its advancing operation.

A pattern path as indicated in FIG. 9C is obtained for the cross bar 12with the feed stroke changing means 7 allowed to retract or contract by100 mm in the cross bar 12's advancing operation and to extend orelongate by 100 mm when it is returned from the downstream to thestand-by position Z.

A patterned path as indicated in FIG. 9D is obtained for the cross bar12 with the feed stroke changing means 7 caused to extend or elongate by100 mm when the cross bar 12 is returning from the stand-by position Zto the upstream and to retract or contract by 100 mm when it is operatedto advance.

This permits the workpiece 14 and the work attracting means 13 to beprevented from interfering with a die or a slide la while the workpiece14 is being transferred. And, the feed stroke may be varied for each ofthe cross bars 12, then the transfer of workpieces 14 becomes stillpossible if the work stations are not equidistantly spaced apart.

Also, if the transfer press path line is varied from P to P' as shown inFIGS. 10A and 10B in accordance with a change in configuration ofworkpieces 14 or a change in height of dies used, the variation of thepath line from P to P' can be effected while controlling the lift means3 with the control means.

Then, raising the lift beams 2 and the cross bar carriers 4 by the liftmeans 3 allows the cross bars 12 to be raised.

Then, since the feed lever 20a remains at a halt, the point 0' at whichthe cross bar carrier 4 and the link member 18 are pivotally connectedtogether assumes a circular motion in a vertical plane about the point 0at which the feed lever 20a and the link member 18 are pivotallyconnected together so that as the lift beams 2 are raised the cross barcarrier 4 may be displaced downstreams. As a consequence, as shown inFIG. 10a an error L does develop in the feed (X-axis) direction at thecross bar 12 supported by the cross bar carrier 4 with the heightdifference between the path lines P and P'.

As pointed out earlier, the error L has heretofore caused a problem torise such that the workpiece 14 is enable to be attracted at apredetermined site to a suction type work attracting means 13. Such aproblem is effectively resolved according to the present invention bypermitting the feed stroke changing means 7 to displace the subsidiarycarrier 4₂ in the feed (X-axis) direction as the path line is changedfrom P to P' so as to eliminate the error L.

More specifically, the control means that has been described has storedtherein a table of corrective values, determined by path lines (P, P', .. . ) which are different in height, with respect to the distance of thecross bar carrier 4 from the point of origin so that as the path line ischanged from P to P', an input of the height the a path line after thechange into the control means will cause the latter to read out of thetable a particular corrective value in distance determined by the heightinput of the path line and to furnish the feed stroke changing means 7with a control signal representing the corrective value.

This causes, as the path line is changed from P to P', the feed strokechanging means 7 to retract or contract as shown in FIG. 10B, permittingthe subsidiary carrier 4₂ to be displaced upstreams by the error L toreduce it to 0, thereby effecting a compensation for the same.

Also, if the path line is changing from P' to P with a resultant shiftupstream of the cross bar carrier 4 to develop the error L in theposition of the cross bar 12 in the feed (X-axis) direction, a controlsignal furnished from the control means causes the feed stroke changingmeans 7 to extend or expand, permitting the subsidiary carrier 4₂ to bedisplaced downstreams so as to reduce the error L to 0, thuscompensating for the same.

FIGS. 11 and 12 illustrate a second embodiment of the present inventionin which the feed stroke means 7 is constituted by a rack (7d) andpinion (7e) arrangement in lieu of the cylinder arrangement previousshown.

More specifically, a rack 7d extending in the feed (X-axis) direction isarranged on the principal carrier 4₁ and supported by rollers 7f andguide members 7g so as to be displaceable in the feed (X-axis)direction.

The downstream side of the rack 7d is connected via the pin 9 to thebracket 4b of the subsidiary carrier 4₂ and the principal carrier 4₁ isprovided with a rotary drive source 7h which may be constituted by aservo motor. The rotary drive source 7h rotating a pinion 7e in meshwith the rack 7d causes the subsidiary carrier 4₂ to be displaced in thefeed (X-axis) direction relative to the principal carrier 4₁ to allowthe feed stroke to be altered.

It should be noted that analogously to the first embodiment the secondembodiment employs an arrangement in which both principal and subsidiarycarriers 4₁ and 4₂ are supported by lift beams 2, the cross bar 12 iscarried by subsidiary carriers 4₂ and the workpiece 14 is operatively.transferred as previously shown and described. Also, in FIGS. 11 and 12the same reference numerals as used in the previous figures are intendedto show the same parts or components.

While the present invention has hereinbefore been set forth with respectto certain illustrative embodiments thereof, it will readily beappreciated by a person skilled in the art to be obvious that manyalterations thereof, omissions therefrom and additions thereto can bemade without departing from the essence and the scope of the presentinvention. Accordingly, it should be understood that the presentinvention is not limited to the specific embodiments thereof set outabove, but includes all possible embodiments thereof that can be madewithin the scope with respect to the features specifically set forth inthe appended claims and encompasses all the equivalents thereof.

What is claimed is:
 1. A feed stroke varying apparatus for a transferfeeder for use in a transfer press having a plurality of work stationsin a press machine body, the transfer feeder having a plurality of crossbars arranged spaced apart from one another in a feed direction andoperative to move two-dimensionally by a feed means and a lift means,and an attractive means carried by each of the cross bars forattractively holding a workpiece and movable therewith for transferringthe workpiece into and from one of the work stations to anothersequentially, the feed stroke varying apparatus comprising:a pair oflift beams adapted to be raised and lowered by said lift means; aplurality of cross bar carriers carried spaced apart from one another bysaid pair of lift beams in the feed direction and each constructed of aprincipal carrier and a subsidiary carrier both suspended from lowersides of said lift beams so as to be capable of reciprocating; acoupling means for interconnecting the principal carriers; a link memberfor connecting to said feed means one of said principal carriers whichis located at a most upstream side thereof; a feed stroke changing meansarranged between a said principal carrier and a said subsidiary carrierfor changing a relative distance therebetween to alter a stroke of feedperformed by said cross bars; and a control means for controlling anoperation of said feed stroke changing means, each of said cross barsbeing detachably bridged across a pair of said subsidiary carriersopposed to each other, said feed means being adapted to reciprocate saidcross bars in the feed direction, said feed stroke changing means beingadapted to alter the feed stroke of said cross bars.
 2. A variable feedstroke feeder apparatus for a transfer feeder as set forth in claim 1,in which said control means is responsive to an error in feed strokeresultant from a change in transfer press path line as caused by achange in height of said cross bars and is operative to act to extendand retract said feed stroke changing means so as to correct said error.